In a conventional wireless communication system using IEEE 802.16e standard, various kinds of broadcasting messages were used. Types of conventional broadcasting messages and information including the broadcasting messages will now be briefly described.
A Downlink Channel Descriptor (DCD) is a Media Access Control (MAC) management message which transmits system information regarding a downlink channel. A MS may receive the DCD and decode downlink burst. An Uplink Channel Descriptor (UCD) is a MAC management message which transmits system information regarding an uplink channel. The MS receives the UCD and then starts transmission of a signal to the uplink channel. ‘MOB-TRF-IND’ is a MAC management message which indicates whether there is downlink traffic that will be transmitted to MSs in a sleep mode and ‘MOB-PAG-ADV’ is a MAC management message which indicates whether there is downlink traffic that will be transmitted to MSs in an idle mode. Further, ‘MOB-NBR-ADV’ is a message which advertises system information of neighboring base stations, ‘LBS-ADV’ is a message which advertises Location Based Service (LBS) information, and ‘Service Identify Information Advertisement (SII-ADV)’ is a broadcasting message which advertises service ID information.
Downlink control channels in an IEEE 802.16m system are briefly described. The downlink control channels contain information necessary for operation of the IEEE 802.16m system. Information on the downlink control channels are hierarchically transmitted on different time scales from a super frame level to an Advanced Air Interface (AAI) subframe level. In a wireless MAN-OFDMA/Advanced Air Interface) operation, a MS is able to access the system without decoding wireless MAN-OFDMA FCH and MAP messages.
A Super Frame Header (SFH), one of the downlink control channels, is transmitted in a state of including necessary system parameters and system configuration information. Particularly, the SFH carries system information necessary for a MS to enter a network. The SFH includes a Primary Super Frame Header (P-SFH) and a Secondary Super Frame Header (S-SFH). The P-SFH is transmitted for each super frame. The S-SFH may be also transmitted for each super frame. The SFH is also called a Broadcast Cannel (BCH) (broadcast channel includes a Primary Broadcast Channel (P-BCH) and a Secondary Broadcast Channel (S-BCH)) and the SFH and BCH are used as terms having the same meaning.
Advanced MAP (A-MAP) carries unicast service control information. The unicast service control information is largely divided into user-specific control information and non-user specific control information. The user-specific control information includes assignment information, HARQ feedback information, and power control information, which are respectively transmitted in an assignment A-MAP, HARQ feedback A-MAP, and power control A-MAP.
FIG. 1 illustrates exemplary positions of A-MAP regions allocated in a frame structure in an IEEE 802.16m system.
FIG. 1 shows A-MAP allocation positions in one frame in the IEEE 802.16m system. Particularly, FIG. 1 shows a case in which the ratio of the number of downlink subframes to the number of uplink subframes is 4:4 in a single frame in a frame structure using Time Division Duplex (TDD). All of A-MAPs in one frame share a region of physical resources, which is called an A-MAP region. The A-MAP region is located in every downlink subframe. Downlink data corresponding to control information included in the A-MAP region may be assigned to resource regions in the subframes corresponding to the A-MAP region.
FIG. 2 shows the structure of an A-MAP region in an IEEE 802.16m system.
Referring to FIG. 2, an A-MAP region 210 includes a non-user specific A-MAP 220, HARQ feedback A-MAP 230, power control A-MAP 240, and assignment A-MAP 250. A non-user specific A-MAP Information Element (IE) is comprised of information that is not assigned to a specific user or users of a specific group, that is, information transmitted to every MS. The HARQ feedback A-MAP 230 includes control information regarding re-transmission request and the power control A-MAP 240 includes power control information for uplink power control of a MS. An assignment A-MAP IE includes information for decoding.
The number of assignment A-MAPs in each assignment A-MAP group is designated by the non-user specific A-MAP IE 220. The assignment A-AMP 250 includes resource assignment information classified into various types of resource assignment IEs (assignment A-MAP IEs). The assignment A-MAP IEs are individually coded and transmitted in a state of including information for one user or users of one group. The assignment A-MAP IEs will be transmitted as minimum LRUs in one minimum LRU A-MAP region 210.
The number of Logically Contiguous MLRUs is determined based on the size of an assignment IE and a channel coding rate and the channel coding rate is selected based on the link condition of a MS. The assignment A-MAPs 250 are grouped based on a modulation and coding selection level and the size of an A-MAP IE. Each assignment A-MAP group includes multiple logically contiguous MLRUs and the number of assignment A-MAPs 250 in each assignment A-MAP group is delivered by the non-user specific A-MAP 220.
As shown in FIG. 2, the A-MAP region 210 in the A-MAP region structure included in one frequency partition is comprised of LAMAP distributed Logical Resource Units (LRUs) configured by Physical Resource Units (PRUs) of symbols) of Nsym symbols.
When an idle mode MS wants to know whether a paging message is transmitted from the A-MAP information shown in FIGS. 1 and 2, the MS has to read scheduling information in every subframe during a paging listening interval. Further, a sleep mode MS has to perform an operation of reading scheduling information in every subframe during a sleep listening interval if the MS wants to know whether a traffic indication (TRF-IND) message is transmitted. Accordingly, if the MS in the idle or sleep mode checks whether a broadcasting message is transmitted through A-MAP, overhead according to decoding of all scheduling information regarding the MS considerably increases.